1. Field
The present invention is related to a method, system and device for distributing in real time data related to three dimensional computer modeled image scenes over a network, and more specifically to a method, system and device for distributing in real time, over a network, texture, geometry and other related three dimensional parameters for said image scenes dependent on an importance value.
2. Discussion of Related Technology
Three dimensional modeled image scenes used for example in virtual reality scenes, in three dimensional “live” modeling as in Computer Aided Design Systems and other types of computer visualization techniques etc., three dimensional geometry parameters and three dimensional objects called textures are defining appearance etc. of objects in a scene or in a series of scenes. The computer data files for complex huge models may be very large and can typically span from several megabytes to gigabytes in size, and may be impractical to distribute over a network with limited bandwidth. Even when there is no real time requirement, the time used for the transfer may be too large to be of practical use.
Another aspect of the client/server rendering problem is the capacity in each client computer. There will always be a limited amount of resources available for rendering purposes, for example a limited amount of allocated memory for the images downloaded to the client computer. In prior art this is usually solved by limiting the file size for downloading, to the capacity of the client computer with the lowest available resources for the task. Therefore, automatic scaling is a problem with prior art solutions, especially scaling to individual client computer requirements and possibilities.
A common technique in real time rendering engines is to use so called mipmap textures. This means that the rendering engine has several copies of each texture stored in decreasing level of detail for each texture. Usually, each level provides half the previous level of detail down to one by one pixel textures. Prior art such as DirectX or OpenGL utilize these mipmap levels to filter between the different levels of detail dependent on a distance between an image capturing device such as a camera or generally speaking, a distance of view from an observer or observation point to an object in a scene. In a three dimensional view, elements closer to the observing point is rendered with more details in the texture than those parts farther away from the observing point. Usually, all the texture levels for all textures must be transferred from a server prior to the rendering of a scene in a client computer. Some prior art solutions transfer only a subset of the mipmaps and utilize filtering to reduce aliasing artifacts in the rendered images.
The common method in prior art for modeling a data set defining scenes for three dimensional visualization, is by utilizing a reference system for a complete scene, sometimes referenced as a global reference system, and by utilizing local reference systems each attached to objects in said scene. In the global reference system, vectors describe shapes and locations of objects while the local reference systems provide polygons for the texture descriptions. To provide enough resolution for a texture, the polygons are defined as floating point numbers. The same texture may be utilized by different objects in a scene. However, the enormous amount of data that the visualization of such three dimensional real time scenes needs, require some trade off between the quality of the visual appearance on the computer display and the amount of data necessary to distribute from a server to a client computer, for example. The known “trade off” techniques as known to a person skilled in the art, does not take into account the visual appearance as such, but assume that distance of view and filtering alone will be a sufficient trade off to provide a workable solution.
In U.S. Pat. No. 6,377,257 B1 with the title: “Method and Apparatus for delivering 3D Graphics in a networked environment”, it is disclosed a solution addressing these matters by providing a seamless continuous rendering options between server-only rendering and client-only rendering. According to this solution, a scene model is partitioned into at least two parts. Initially, said first part comprising initial geometry description of said scene is downloaded to the client computer from the server. While the client computer executes the rendering based on the initial file comprising said first part, the server computer may continue to download said second part of said scene, thereby for example providing more details in the scene when the client computer starts rendering said second part. However, the speed of the downloading is improved, but to be able to achieve a necessary level of details in the visualization may require a substantial amount of further downloads of a specific scene.
Practical use of for example Computer Aided Design Systems using three dimensional real time visualization techniques, for example to certify and verify a design, require another type of trade off to provide a workable solution. It is necessary to control the level of detail to be able to evaluate a design correctly in every detail.
In other real time three dimensional visualization systems and applications, the speed of rendering and quality of images may be mandatory for the usefulness of such systems. Therefore, there is a need for a method, system and device that can improve the visual quality and speed of rendering in such real time three dimensional visualization systems.